1. Technical Field
The present invention relates to a wheel reaction force detecting apparatus capable of detecting a reaction force on a wheel fixed to a hub rotatably supported through a hub bearing.
2. Related Art
Various types of information are needed to control recent cars, and a sensor device disposed on a hub to which a wheel is fixed, the hub being rotatably supported through a hub bearing, is proposed (see Japanese Unexamined Patent Application Publication (JP-A) No. 2006-226683). The sensor device described in JP-A No. 2006-226683 includes a load sensor for detecting a reaction force on a wheel, a shim member, and a sensor holding member. The load sensor is disposed inside an axial through hole in a flange in a vehicle-body track member fixed on a vehicle body, the shim member is disposed between the load sensor and the inner surface of the axial through hole, and the sensor holding member is disposed between the load sensor and the outer surface of the axial through hole. Preload on the load sensor is adjustable by changing the thickness of the shim member.
In the hub equipped with the known sensor device, the inner race is rotatably disposed inside the track member through balls (rolling elements), an inner shaft is disposed inside the inner race, the flange is disposed on a second end of the inner shaft, and the wheel is fixed to the flange.
The inner race in the hub equipped with the known sensor device is fixed by a nut screwed to an end of the inner shaft. If the nut is loosened, play of the balls (rolling elements) sandwiched between the vehicle-body track member and the inner race is increased. That may degrade the accuracy of detecting a wheel reaction force on the wheel by the load sensor. If the stiffness of the bearing including the inner race, balls, and track member decreases due to age, the accuracy of detecting a wheel reaction force by the load sensor may also be degraded.